This invention generally relates to intravascular catheters, particularly catheters for use in percutaneous transluminal coronary angioplasty (PCTA) or stent delivery.
In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient""s coronary anatomy where the balloon of the dilatation catheter is properly positioned within the stenosis to be dilated. The balloon is then inflated to a predetermined size with radiopaque liquid at relatively high pressures (generally 8-18 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient""s coronary anatomy to dilate additional stenoses.
The distal tip of an intravascular catheter may be constructed to have non-traumatic characteristics to minimize damage when passing through a body lumen. A typical non-traumatic tip is formed from a short tubular member made of relatively soft polymeric material which is secured to the distal tip of the tubular distal extremity of the catheter. However, this construction does not always eliminate injury to the luminal lining. For example, the leading edge of the distal skirt of the balloon which extends radially outward can cause intimal injury even though it may be somewhat tapered. Moreover, securing a distal lip made from softer material or otherwise designed to collapse so as to avoid intimal injury, complicates the manufacturing procedure and increases its costs.
What has been needed and heretofore unavailable is a simple, inexpensive method for forming a nontraumatic distal tip. The present invention satisfies this and other needs.
This invention is directed to a distal tip construction for intraluminal catheters which has an improved non-traumatic characteristics and which is simple and inexpensive to produce.
The catheter of the invention generally has an elongated shaft with a proximal end, a distal end, a guidewire lumen extending through at least the distal portion of the catheter and a port in the distal end in fluid communication with the guidewire lumen. The elongated catheter has a tubular distal extremity which defines the guidewire lumen and which has an expanded portion with outer dimensions greater than a proximally adjacent unexpanded portion. Preferably, the tubular distal extremity tapers in the direction distal to the expanded portion to a smaller outer diameter at the distal end thereof which defines the port therein.
In one presently preferred embodiments of the invention, the catheter is a dilatation catheter having a balloon on a distal shaft section with an inner tubular member extending through and distal to the balloon which defines the guidewire lumen. The portion of the inner tubular member extending distal to the balloon is expanded in accordance with the present invention with the distal skirt of the balloon secured to an unexpanded portion of the inner tubular member proximally adjacent to the expanded portion. The distal skirt of the balloon is preferably sealingly bonded to the exterior of the unexpanded portion of the inner tubular member in a suitable manner such as by fusion or adhesive bonding. The expanded portion of the inner tubular member which extends distal to the distal skirt of the balloon preferably has outer dimensions which are essentially the same as or slightly larger than the outer dimensions of the distal skirt of the balloon so as to present a non-traumatic exterior to the interior of the body lumen in which the catheter is advanced.
The distal tubular extremity may be formed by placing it within a molding surface, such as a sheath, with interior dimensions the same as the desired dimensions of the expanded portion of the distal tubular extremity. The interior of the distal tubular extremity is then subjected to fluid pressure and the exterior to heat which causes the heated portion to soften or melt thereby expanding to the interior dimensions of the molding surface. The proximal portion of the distal tubular extremity, which is not to be expanded, may be supported exteriorly and not subjected to elevated temperatures so that it does not expand. The part of the distal tubular extremity distal to the expanded portion is likewise not expanded in a similar manner during the manufacturing procedure.
The expanded portion of the tubular distal extremity of the catheter ranges in length from about 0.1 to about 1.0 cm, preferably about 0.2 to about 0.5 cm. The overall length of the tubular distal extremity of the catheter which extends distal to the distal balloon skirt in the aforesaid presently preferred embodiment ranges from about 0.2 to about 1.5 cm, preferably about 0.3 to about 0.7 cm. The inner diameter or dimensions of the guidewire lumen extending through the expanded portion ranges from about 0.018 to about 0.035 inch (0.46-0.89 mm), preferably about 0.021 to about 0.025 inches (0.53-0.64 mm). The inner transverse dimensions of the guidewire lumen proximal to the expanded portion for a 3 mm balloon is about 0.013 to about 0.023 inches (0.33-0.58 mm), preferably about 0.016 to about 0.019 inch (0.41-0.48 mm) for a 0.014 inch (0.36 mm) guidewire. The guidewire lumen distal to the expanded portion is preferably tapered from the inner diameter of the expanded portion to transverse dimension slightly greater than the transverse dimensions of the guidewire to be passed therethrough. The wall thickness of the tubular distal extremity will vary depending upon the polymeric material from which the tubular member is made. The wall thickness of the expanded portion will usually be less than the unexpanded portion due to the expansion thereof by blowing unless the wall thickness of the portion to be expanded is initially greater than the portion which is not to be expanded.
The present invention provides an improved non-traumatic distal tip for intravascular catheters, which has gradual distal transitions in both profile and stiffness. This is particularly advantageous in balloon dilatation catheters where the distal skirt of the balloon can be secured to the unexpanded portion of the distal tubular extremity of the catheter proximal to the expanded portion so as to present a distal tip with a smooth, uniform exterior.
These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.